The present invention relates to an apparatus for measuring out pulverulent materials, in which a screw is used.
Numerous devices for conveying and measuring out pulverulent materials are known. For example, measuring devices employing vibrations, automatic balances equipped with endless conveyor belts, funnels with a perforated base equipped with bladed wheels and the like have been described, for example in the periodical Fette, Seifen, Anstrichmittel, 56, No. 5, 1954, p. 321 to 325.
It is also known to use screw conveyors of various types for conveying pulverulent materials as disclosed in the article by H. W. Cremer and S. B. Watkins in Chemical Engineering Practice, 1957, vol. 3, p. 406 to 410. Devices of this type can also be suitable, in some cases, for the approximate measuring out of pulverulent materials.
Nevertheless, if the materials to be measured out are in the form of sticky powders or powders with mediocre flow properties, or if they are in the form of granules which have a tendency to agglomerate, it often happens that the agglomeration of the material between the teeth of the screw leads to clogging and blocking of the latter. It is then necessary to dismantle the apparatus in order to clean it. Moreover, the measuring is wholly lacking in precision.
These disadvantages are particularly objectionable when such an apparatus is intended to feed a reactor in a uniform manner with a catalyst or a reactive solid possessing these mediocre morphological characteristics. In fact, uneven feeding can, in this case, have a very detrimental effect on the way in which the chemical reaction takes place, on the yield of the product obtained and on the quality of the latter.